Field of the Invention
The present invention relates to a fundus imaging apparatus and method, and more particularly, to a fundus imaging apparatus and an imaging method for scanning a fundus with irradiation light to obtain a fundus image.
Description of the Related Art
In recent years, as a device for taking a fundus image, the use of a fundus imaging apparatus for scanning with irradiation light to take a fundus image, such as a confocal scanning laser ophthalmoscope (SLO) for acquiring a still or moving image of high resolution, has been popular. In such a fundus imaging apparatus, some time is required from the start to the end of the imaging. Therefore, the imaging is susceptible to involuntary eyeball movements called flicks, eyeball movements due to poor fixation, or the movement of the eye accompanying the movement of the face. This adds more importance to fundus tracking for tracking the movement of a fundus (U.S. Pat. No. 7,758,189).
In addition, in such an ophthalmologic imaging apparatus, higher resolution has been achieved by using a higher NA of an irradiating laser in recent years. However, when taking a fundus image, it is necessary to take the image through the optical system of the eye such as the cornea and crystalline lens. Along with achieving higher resolution, the influences of aberrations of the cornea and the crystalline lens on image quality of a taken image have become larger. Therefore, studies have been made on an AO-SLO (Adaptive Optics—Scanning Laser Ophthalmoscope) and an AO-OCT (Adaptive Optics—Optical Coherence Tomography), in which aberration of the eye is measured, and an adaptive optics (AO) as a compensation optical system for correcting the aberration is incorporated in the optical system. For instance, “Y. Zhang et al, Optics Express, Vol. 14, No. 10, May 15, 2006” describes an example of the AO-OCT. In the AO-SLO and the AO-OCT, a wavefront of the eye is usually measured by the Shack-Hartmann wavefront sensor method, and a variable shape mirror or a spatial phase modulator is driven so as to correct the measured wavefront. By taking the fundus image through the variable shape mirror, or the spatial phase modulator, the AO-SLO and the AO-OCT can take a high resolution image.
Along with an improvement of the imaging resolution of the imaging apparatus, it is necessary to also improve tracking accuracy for tracking a movement of the fundus to be imaged. However, because the movement of the eye is complicated, it is difficult to perform high accuracy tracking simply by using the related-art optical axis adjustment unit used in U.S. Pat. No. 7,758,189.